Liquid crystalline polybenzoxazines for manufacturing of technical textiles: Water repellency and ultraviolet shielding

Herein, the presented approach was investigated a unique technique for manufacturing water repellent/UV-protective cotton fabrics through in-situ/thermal polymerization of benzoxazine (BZs) within cotton matrix. Two BZs abbreviated as Ph-p-BZ and Ph-o-BZ were initially synthesized, and their chemical formulas were verified with FTIR, 1HNMR, and 13CNMR spectral mapping data. For Ph-p-BZ, the endothermic peak was observed at 65 ᵒC, to indicate its highly/purified crystalline structure. DSC data for poly-(Ph-p-BZ) and poly-(Ph-o-BZ) showed that, their high Tg was estimated at 210 ᵒC and 195 ᵒC, respectively, due to their highly crystalline/cross-linked network structure. In-situ/thermal polymerization of Ph-p-BZ and Ph-o-BZ as within cotton matrix was subsequently proceeded. Contact angle was observably increased to 125.0° for the fabric coated with four layers of poly-(Ph-p-BZ) (cotton modified with four layers of poly-(Ph-o-BZ); 120.3°). Wetting of water droplets was not significantly observed even after 8 min. Ultraviolet protection factor (UPF) was significantly increased from 1.4 for untreated cotton to 37.9 and 48.2 after modification of cotton with 4-layers of poly-(Ph-o-BZ) and poly-(Ph-p-BZ) polymers, respectively. Eventually, poly-benzoxazines derivatives could be applicable for manufacturing of water repellent/UV-protective fabrics that might be beneficial for military clothes.